Backyard stuff won't download.

@DerpDog114  What country are you in, and do you have an underage account?  (Don't tell me how old you are; just yes or no will be fine.)  Can you redeem the pack here?

https://www.ea.com/games/the-sims/the-sims-4/store/addons/the-sims-4-backyard-stuff

If it works, you should see Backyard Stuff in your EA App game library, under Sims 4 > Manage > Manage add-ons.  Let me know whether it appears, and if so, whether you can download it from there.

I wouldn't recommend redeeming the pack in Steam because that would mean you'd need to uninstall the EA App version of Sims 4 and reinstall the game through Steam.

@mrsnicell  If you'd like help with your issue, please create your own thread describing the problem.  Please also run a dxdiag and attach it to your post.

https://help.ea.com/en-us/help/pc/how-to-gather-dxdiag-information/